Opsin labeling with galactose was found to occur at a constant rate throughout the diurnal cycle. Thus, neither synthesis nor intracellular transport of opsin appears to exhibit any circadian rhythm. Iodination of bovine pigment epithelium followed by SDS gel electrophoresis revealed a reproducible pattern of plasma membrane proteins, several of which were also labeled on incubation of eyecups with radioactive glucosamine. Thus these are glycoproteins which may mediate recognition of outer segment membranes in preparation for phagocytosis.